In disease states, such as emphysema and aneurysmal degeneration, the degradation of elastin fibers that characterizes these conditions is accompanied by repair processes that are insufficient and fail to prevent disease progression. Towards this goal our objectives are to regenerate elastin in tissue culture systems by crosslinking recombinant tropoelastin (rTE) into damaged elastin and to characterize the effectiveness of this regeneration by assessing the functional mechanical, biochemical, and ultrastructural properties. Our central hypothesis is that elastin can be regenerated in vitro and in vivo by administering rTE to damaged elastin, thereby restoring, at least in part, the pre-existing elastin fiber organization and its mechanical properties. Such repair might prevent mechanical forces from causing failure of the remodeled matrix at loci of stress concentrations. Aim 1.To identify the separate contributions of elastin, proteoglycans, collagens, and cells to the macroscopic mechanical properties of elastogenic cultures. This will be carried out in well-defined cultures by manipulating the amount of elastin, fibrillar collagen, proteoglycans or by generating cell-free matrices. This will provide essential information on the structural and mechanical properties of the components of extracellular matrices and provide the baseline information for this in vitro model system. Aim 2. To assess the changes in functional mechanical, biochemical, and ultrastructural properties of the defined elastogenic cultures from Aim 1 during and after treatment with elastases to degrade elastin and proteoglycans or with non-elastolytic enzymes to digest primarily collagen or proteoglycans. The cultures will then be monitored as the endogenous smooth muscle cells effect repair. The information will shed light on how enzymatic injury degenerates structure and mechanical function and the effectiveness of endogenous repair processes. Aim 3. To determine the mechanical, biochemical and ultrastructural properties of rTE mediated regeneration of elastase-treated matrices in the presence or absence of endogenous tropoelastin production.